Information equipment such as a laptop personal computer and a portable telephone includes one that includes a main body unit with input keys and a display unit in which the display unit is rotatably connected to the main body unit with a hinge mechanism, and is used by opening and closing the display unit. FIG. 1A illustrates the location of a hinge device 10 in a laptop personal computer 1 including a main body unit 1M and a display unit 1D. FIG. 1B is an enlarged view of a section of the hinge device 10 in the laptop personal computer 1 illustrated in FIG. 1A. FIG. 1C illustrates the hinge device 10 taken out of the laptop personal computer illustrated in FIG. 1B.
The hinge device 10 illustrated in FIG. 1C includes a main body connector 2 and a display connector 3 as illustrated in FIG. 1D. A hinge rotating shaft 4 provided in the display connector 3 is rotatably held on a bracket 5 protruded from the main body connector 2. The hinge rotating shaft 4 is inserted through a ring-shaped friction plate 6 and then inserted through a holding hole 5H of the bracket 5. Between a free end 4E of the inserted hinge rotating shaft 4 and the bracket 5, a ring-shaped friction plate 6 and multiple disc springs 7 are inserted from the bracket 5 side. Then, a pressure plate 8 is attached to the free end 4E of the hinge rotating shaft 4 in a state where the disc springs 7 are compressed. Thus, a hinge torque generator 9 is formed. Note that the friction plate 6 is fixed to the hinge rotating shaft 4 using a key groove or the like, and is rotated in synchronization with the rotation of the hinge rotating shaft 4.
The hinge torque generator 9 uses spring force generated by the compression of the disc springs 7 with the pressure plate 8 to allow a side surface of the friction plate 6 adjacent to the disc springs 7 to come into pressure contact with one side surface of the bracket 5 on the main body connector 2, and also allow a side surface of the friction plate 6 adjacent to the main body connector 2 to come into pressure contact with the other side surface of the bracket 5. The pressure contact between the two friction plates 6 and the bracket 5 on the main body connector 2 causes friction force between the main body connector 2 and the display connector 3, thereby generating hinge torque. The hinge torque can hold the display unit 1D at a given open angle when the display unit 1D is opened relative to the main body unit 1M (free-stop function).
Note that Japanese Laid-open Patent Publication No. 2004-246497 discloses an information processor that is a laptop personal computer as illustrated in FIG. 1A and configured to reduce hinge torque upon receipt of a friction resistance reduction instruction from a user, when changing the open angle of the display unit from the given open angle to another open angle.
Meanwhile, there has recently been put to practical use a laptop personal computer 1 equipped with a touch panel display 1T in a display unit 1D and capable of menu selection, character input and the like by touch operations to the touch panel display 1T as illustrated in FIG. 2A.
The touch panel display 1T is hereinafter simply described as the touch panel 1T. In such a laptop personal computer 1, menu selection, character input and the like are performed by touching the touch panel 1T in the display unit 1D.
However, the hinge device 10 having the structure described with reference to FIGS. 1A to 1D, the hinge torque generator 9 has a spring element, a torsion element and the like. Therefore, when a touch operation is performed on the touch panel 1T in the display unit 1D, a touch operation torque acting on the hinge rotating shaft 4 in the hinge device 10 rotates the hinge rotating shaft 4, causing the display unit 1D to vibrate in opening and closing directions. When the display unit 1D vibrates during the touch operation to the touch panel 1T as described above, there is a problem that steadiness is lost and thus operability of the touch operation is impaired.
FIG. 2B illustrates a configuration of a vibration measurement system 90 configured to measure vibration of the display unit 1D when a touch operation is performed at a position distant from the hinge rotating shaft 4 by a predetermined distance L, for example, 200 mm on the touch panel 1T in the laptop personal computer 1 illustrated in FIG. 2A. The vibration measurement system 90 includes a laser generator 91, a laser receiver 92 and a vibration detector 93 connected to the laser receiver 92. During measurement, the back side of the display unit 1D is irradiated with laser light from the laser generator 91, and a touch operation is performed in a state where reflected light is received by the laser receiver 92. Then, a degree of vibration of the display unit 1D during the touch operation is actually measured by the vibration detector 93 measuring a change in reflection angle of the laser light in this state.
FIG. 2C is a graph illustrating an oscillatory waveform of the display unit 1D, which is measured by the vibration detector 93 illustrated in FIG. 2B, during a touch operation on the touch panel 1T. The first peak of the waveform is displacement of the display unit 1D due to the touch operation, and the oscillatory waveform after the second peak is residual vibration of the display unit 1D after a finger is removed from the touch panel 1T. As can be seen from FIG. 2C, the vibration of the display unit 1D lasts several seconds with decreasing displacement even after the touch operation is finished and the finger is removed from the touch panel 1T.
In order to suppress the vibration of the display unit 1D during the touch operation on the touch panel 1T as described above, a countermeasure is conceivable to increase the friction force of the hinge torque generator 9 illustrated in FIGS. 1C and 1D. However, when the friction force of the hinge torque generator 9 is increased, a large force has to be used to open and close the display unit 1D. For this reason, it feels heavy to open and close the display unit 1D, leading to a new problem of poor operability.